I have a couple of windows pc's and a mac at home and don't like the idea that i have to have accounts on all the computer for each user at home. Is there a simple domain, no tech-net subscription for win server, that I can put my windows pc's (Win7, win8, WinRT), and mac (OSX) on? I'm cool with running some sort of *nix as I have a plug pc that is not being used at the moment. I'm not looking for the answer "Buy windows serer". I would write a custom GINA for my windows PC's before I do that...
You should look into Windows Home Server 2011. It is based off of Windows Server 2008R2 and can do all of what you're looking for including more; file sharing server, nightly incremental backups of your computers.
I know that you said that you're not looking for buying a Windows Server, but this is only $50 and is packed with a lot of features. (http://www.howtogeek.com/57729/how-to-make-windows-home-server-into-a-domain-controller/)
This would probably be a good method. You would just want to make sure that your versions of windows support joining a domain. Ie. Windows 7 Home doesn't support joining a domain.